ASHINGTON — The politics of the health care debate have become byzantine. You have conservatives upset the Republican bill isn’t aggressive enough, moderates worried their constituents could be at risk, leadership eager to push the legislation through so they can move on, and a President Trump-shaped enigma at the center.

Every policy decision tips the scales, and leadership has struggled to find the right balance.

It’s a perilous push-and-pull and a lot for everybody else to keep track of. So let’s make it simple.

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STAT asked a half-dozen lobbyists and observers to name the most important people in the debate to watch right now. Of course, House Speaker Paul Ryan (the face of the plan) and Senate Majority Leader Mitch McConnell (who must contend with complex rules and a slim margin for error to pass the bill) made almost every list.

But who else? Coupled with our own observations, these are the other key players.

Senator Lamar Alexander of Tennessee

Susan Walsh/AP

Alexander is an experienced policy wonk who chairs the powerful health committee, and he has been clear-eyed about the challenges of overhauling Obamacare.

All the legislating is in the House right now, but lobbyists expect Alexander to take a leading role once the bill moves to the Senate — especially if it needs some work in order to win over some of his skeptical colleagues.

Speaking of which …

Senator Tom Cotton of Arkansas

Mark Wilson/Getty Images

Four more moderate senators from Medicaid expansion states are on record with their concerns about the House plan. Conservative agitators like Senator Rand Paul of Kentucky have attacked it from the other angle. But Cotton, the junior senator from Arkansas, is perhaps the most interesting swing vote because he can fit into both camps.

Arkansas expanded Medicaid (pioneering a unique model for doing so that led other red states to get onboard) and has seen one of the largest drops in its uninsured rate under Obamacare. Cotton is on the record with his worries that the Republican plan would lead to coverage losses.

But unlike, say, Rob Portman of Ohio, one of the moderate senators with Medicaid concerns, Cotton has also been a conservative darling for much of his career. He’s echoed some of the criticisms we’ve heard from Paul and the Freedom Caucus, that the bill would not actually lower costs either.

Congressman Jim Jordan of Ohio

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Jordan helped found the Freedom Caucus, a group of 40 or so arch-conservatives in the House who often vote as a group and have enough votes to block a bill if they unite against it. He is no longer its official leader — that’s now Mark Meadows of North Carolina — but he remains an influential voice inside the caucus.

Those 40-odd members represent the most immediate threat to the GOP bill. Jordan and his compatriots are arguing that the plan doesn’t go far enough in repealing Obamacare and that it would increase insurance premiums. They are demanding some concessions, though granting them could endanger moderate votes.

That is the inherent tension for GOP leaders for every big issue, on Medicaid as well as the tax credits people would use to buy insurance. Swing the bill too much in one direction to satisfy one wing of their conference and they risk upsetting the other.

Leadership is betting that no stalwart conservative would actually vote against undoing a law they revile when the time comes. But if the Freedom Caucus sticks to its convictions, the legislation might not even get to the Senate.

CBO Director Keith Hall

Alex Wong/Getty Images

The Congressional Budget Office, which provides the official analysis of how many people the bill would cover and how much it would cost, has already demonstrated its awesome political power. After its report Monday that 24 million more people would be uninsured by 2026 under the GOP plan, Democrats had a potent talking point and an increasing number of Republicans seemed skittish.

Democrats constantly engaged with CBO (and anxiously awaited updates) as they tweaked Obamacare before its passage. If and when the GOP alters its plan, the office will update its estimates and their numbers will continue to define the debate.

President Trump

Nicholas Kamm/AFP/Getty Images

It sounds obvious, but it can’t be said enough: Trump could be decisive if he really invests in pushing the bill through. He’s the president of the United States, after all, and usually more popular among the Republican base than any individual member of Congress.

But he would have to commit, using the bully pulpit and his self-professed negotiating skills to wrangle Republicans into line.

The problem right now is that various factions seem to see whatever they want to see in Trump. Many of his top aides are firmly supporting the House bill. But other reports have leaked out that Trump is open to changes to appease the conservative wing of his party and the president himself said the House bill was open for “review and negotiation.”

Nobody has reason to back down yet, because they all have reason to believe Trump is actually on their side.